[1] According to traditional accounts, Thomas the Apostle sailed to the Malabar region in 52 AD and introduced Christianity to the area.
[citation needed] The earliest known source connecting the apostle to India is the Acts of Thomas, likely written in the early 3rd century, perhaps in Edessa.
A number of 3rd- and 4th-century Roman writers also mention Thomas' trip to India, including Ambrose of Milan, Gregory of Nazianzus, Jerome, and Ephrem the Syrian, while Eusebius of Caesarea records that Clement of Alexandria's teacher Pantaenus from Alexandria visited a Christian community in India using the Gospel of Matthew in Hebrew language in the 2nd century.
[10][11] Byzantine traveller Cosmas Indicopleustes wrote of Syrian Christians he met in Malabar and Sri Lanka in the 6th century.
[15] During the Crusades, distorted accounts of the Saint Thomas Christians and the Nestorian Church gave rise to the European legend of Prester John.